Mast and carriage for a lift truck

ABSTRACT

A lift truck incorporates a pair of fixed, laterally spaced apart upright channel members the edge flanges of which are directed inwardly. A pair of interconnected elongated members are associated with these fixed channel members by means of a pair of top rollers mounted to the fixed channel members and positioned adjacent single edge flanges of the elongated members, and a pair of bottom rollers mounted to the elongated members and disposed within the channel members, the edge flanges defining proper cutout portions to allow such positioning of the rollers. The rolling portions of the top rollers are actually in rolling contact with angled portions of the elongated members, and the rolling portions of the bottom rollers are actually in rolling contact with angled portions of the fixed channel members. The cutout portions are so sized, in relation to the rollers associated therewith, that the elongated members cannot be applied to or removed from the fixed channel members with all rollers in place. The movable elongated members further comprise laterally spaced apart movable uprights with which a fork carriage is associated. A first pair of rollers is mounted to the frame of the fork carriage. Such rollers are rollingly associated with one movable upright. A second pair of rollers is mounted to the frame of the fork carriage. These rollers are rollingly associated with the other movable upright. Another roller is mounted to the fork carriage frame with its axis between the axes of the first pair of rollers, and positioned to contact the rear portion of the one movable upright. Yet another roller is mounted to the frame of the fork carriage, with its axis between the axes of the second pair of rollers, and is positioned to contact the rear portion of the other movable upright. Such means allow for raising and lowering the fork carriage relative to the movable upright, meanwhile providing positive forward, rearward, and lateral location of the fork carriage relative thereto.

ii ite taes ate Wagner et al.

Bee. 3, i974 MAST AND CARRIAGE FOR A LIFT TRUCK [75] Inventors: RichardA. Wagner, Euclid; Paul A.

Reid, Mentor; Edward G. Teutsch,

Willoughby; Milford D. Mcveen, Highland, all of Ohio [73] Assignee:Towmotor Corporation, Mentor,

Ohio

[22] Filed: Feb. 8, v1973 21 1' Appl. No.: 330,890

[52] US. Cl. 187/9 [51] Int. Cl. B661) 9/20 [58] Field of Search 187/9;212/46 B 56] References Cited UNITED STATES PATENTS 2,456,320 12/1948Repke 187/9 2,643,162 6/1953 Barr 2,936,047 5/1960 Quayle 187/93,506,092 4/1970 Shinoda et al. 187/9 3,556,247 l/l97l Shinoda et al.187/9 Primary Examiner-Robert B. Reeves Assistant ExaminerHadd LaneAttorney, Agent, 0r'FirmPhillips, Moore, Weissenberger, Lempio 8LStrabala [57] ABSTRACT A lift truck incorporates a pair of fixed,laterally spaced apart upright channel members the edge flanges of whichare directed inwardly. A pair of interconnected elongated members areassociated with these fixed channel members by means of a pair of toprollers mounted to the fixed channel members and positioned adjacentsingle edge flanges of the elongated members, and a pair of bottomrollers mounted to the elongated members and disposed within the channelmembers, the edge flanges defining proper cutout portions to allow suchpositioning of the rollers. The rolling portions of the top rollers areactually in rolling contact with angled portions of the elongatedmembers, and the rolling portions of the bottom rollers are actually inrolling contact with angled portions of the fixed channel members. Thecutout portions are so sized, in relation to the rollers associatedtherewith, that the elongated members cannot be applied to or removedfrom the fixed channel members with all rollers in place. The movableelongated members further comprise laterally spaced apart movableuprights with which a fork carriage is associated. A first pair ofrollers is mounted to the frame of the fork carriage. Such rollers arerollingly associated with one movable upright. A second pair of rollersis mounted to the frame of the fork carriage. These rollers arerollingly associated with the other movable upright. Another roller ismounted to the forkcarriage frame with its axis between the axes of thefirst pair of rollers, and positioned to contact the rear portion of theone movable upright. Yet another roller is mounted to the frame of thefork carriage, with its axis between the axes of the second pair ofrollers, and is positioned to contact the rear portion of the othermovable upright. Such means allow for raising and lowering the forkcarriage relative to the movable upright, meanwhile providing positiveforward, rearward, and lateral location of the fork carriage relativethereto.

19 Claims, 10 Drawing liigures,

55 p qnntmmin'nr m PATENTL 31974 SHEET 1 0F 6 SHEET 2 OF 6 PATENTEL @51331974 PATENIEL DEC 31974 SIEEI 3 OF 6 PATENTEL EB 31914 3,851,732

saw u or e- PATENTELBEB 31m SHEET 8 0F 6 MAST AND CARRIAGE FOR A LIFTTRUCK BACKGROUND OF THE INVENTION This invention relates to mast andcarriage assemblies for a lift truck, and more particularly, to such anassembly which provides a pair of elongated members extensible relativeto a pair of fixed channel members, and a fork carriage movablyassociated with'the pair of elongated members.

Inthe normal fork-type lift truck, the fork thereof is carried by avertically extensible mast assembly located at the forward end of thetruck. Such fork engages a load in a lower position and is thereafterraised to a desired elevation, in which position such load istransported to a desired location, lowered, and unloaded. Such a mastassembly for supporting a fork carriage preferably includes means forits vertical extension so as to maintain minimum vertical retractedheight, while also providing maximum elevation of the fork carriage.

In general, such extensible mast assemblies of known construction haveincluded a stationary assembly fixed to the truck and a movable sectionincluding a pair of slidingly extensible rail members movable relativeto the stationary assembly, and a fork carriage movably associated withapair of slidingly extensible rail members. Examples of such structuresare US. Pat. No. 2,428,223 to Johnson, US. Pat. No. 2,791,292 to Quayle,US. Pat. No. 2,505,009 to Schroeder, US. Pat. No. 2,918,143 to Shaffer,US. Pat. No. 3,213,967 to Hastings et al., US. Pat. No. 3,506,092 toShinoda et al., US. Pat. No. 2,759,562 to Ulinski. (Of more generalinterest are US. Pat. No. 3,362,503 to Stoilov, US Pat. No. 3,556,247 toShinoda et al., and US. Pat. No. 2,298,196 to Cochran.)

Such previous structures have maintained minimum retracted height andprovided means for elevating the fork carriage thereof above the normalvertical dimension of the stationary mast portion.

The present invention improves upon the general features and concepts ofthe extensible mast structure.

SUMMARY OF THE INVENTION mast assembly in a lift truck which includesrollers which may be easily and properly positioned for proper bearingof eccentric loading, meanwhile insuring smooth operation under this andall other conditions.

It is a still further object of this invention to provide a mastassembly in a lift truck which, while fulfilling the above objects, issimple in design and manufacture.

Broadly stated, the invention comprises a mast assembly for a truck orthe like. Such mast assembly comprises first and second upright,laterally spaced channel members each defining a base portion andforward and rearward parallel edge flange portions extending from thebase portion and generally perpendicular thereto, with the flangeportions of each channel member disposed toward the other channelmember. First and second interconnected elongated members are positionedinwardly of the first and second channel members respectively andmovable therealong, the first elongated member defining a base portionand a single edge flange portion extending from said base portion andgenerally perpendicular thereto, and disposed toward the first channelmember and between the forward and rearward flange portions of the firstchannel member and adjacent the rearward flange portion thereof. Thesecond elongated member defines a base portion and a single edge flangeportion disposed toward the second channel member and between theforward and rearward flange portions of the second channel member andadjacent the rearward flange portion thereof. First and second bottomrollers are mounted to the lower ends of the first and second-elongatedmembers respectively, the single flange portions of the first and secondelongated members defining cutout portions through which portions of thefirst and second top roller respectively extend, with the first bottomroller positioned between the forward and rearward flange portions ofthe first channel member, with the rolling portions of the first bottomroller adjacent the forward and rearward flange portions of the firstchannel member, and further with the second bottom roller positionedbetween the forward and rearward flange portions of the second channelmember, with the rolling portions of the second bottom roller adjacentthe forward and rearward flange portions of the second channel member.First and second top rollers are mounted to the upper ends of the firstand second channel members respectively, with the forward flangeportions of the first and second channel members defining cutoutportions through which portions of the first and second top rollersrespectively extend, with the rolling portion of the first top rolleradjacent the single flange portion of the first elongated member, andwith the rolling portion of the second top roller adjacent the singleflange portion of the second elongated member. Further included is afork carriage comprising a frame and a pair of for wardly extendingarms. First and second rollers are mounted to the fork carriage frameand are rollingly associated with the first elongated member, with theaxis of the second roller being below the axis of the first roller.Third and fourth rollers are mounted to the fork carriage frame and arerollingly associated with the second elongated member, with the axis ofthe fourth roller being below the axis of the third roller, allowingmovement of the fork carriage along the elongated members upwardly anddownwardly, meanwhile providing positive forward and rearward locationof the fork carriage relative to the first and second elongated members.A fifth roller is mounted to the fork carriage frame and is positionedwith its axis below the axis of the first roller and above the axis ofthe second roller. A sixth roller is mounted to the fork carriage frameand is positioned with its axis below the axis of the third roller andabove the axis of the fourth roller, the fifth and sixth rollers beingin contact with rear portions of the first and second elongated membersrespectively, to provide positive lateral location of the fork carriagerelative to the first and second elongated members.

BRIEF DESCRIPTION OF THE DRAWINGS These and other objects of theinvention will become apparent from the study of the followingspecification and drawings, in which:

, FIG. 1 is a perspective view of a lift truck incorporating theinventive mast and carriage assembly;

FIG. 2 is a front elevation, with portions broken away, of a portion ofthe mast and carriage assembly;

FIG. 3 is a view taken along the line Ill-III of FIG. 2;

FIG. 4 is a perspective view of channel member structure of theassembly;

FIG. 5 is a perspective view of the elongated member structure of theassembly;

FIG. 6 is a perspective view of a portion of the fork carriage of theassembly;

DESCRIPTION OF THE PREFERRED EMBODIMENT Shown generally in FIG. I is amast assembly 26 in association with a truck 22. Such mast assemblyincludes a pair of longitudinal, upright, laterally spaced channelmembers 24,26 which are fixed to the body of the truck 22. These channelmembers 24,26 are rigidly connected together by cross braces 30, asshown in FIG. 4. As best shown in FIGS. 4 and 8, channel member 24defines a base portion 32 and forward and rearward parallel edge flangeportions 34,36 extending from the base portion 32 and generallyperpendicular to said base portion 32. Similarly, channel member 26defines a base portion 38 and forward and rearward parallel edge flangeportions 40,42 extending from the base portion 38 and generallyperpendicular to said base portion 38. As will be seen, the flangeportions 34,36 are disposed toward the channel member 26, and the flangeportions 40,42 are disposed toward the channel member 24.

Longitudinal elongated members 44,46 are rigidly interconnected by crossbraces 48 and are positioned inwardly of the channel members 24,26respectively (FIG. 8). The elongated member 44 defines a base portion 50and a single edge flange portion 52 which extends from the base portion50 and is generally perpendicular to the base portion 50. Said flangeportion 52 extends toward the channel member 24 and is disposed betweenforward and rearward flange portions 34,36 and adjacent the rearwardflange portion 36. Similarly, the elongated member 46 defines a baseportion 54 and a single edge flange portion 56 which extends from thebase portion 54 and is generally perpendicular to the base portion 54.Said flange portion 56 extends toward the channel member 26 and isdisposed between the forward and rearward flange portions 40,42,adjacent the rearward flange portion 42.

Bottom roller 58 is mounted to the lower end of the elongated member 44,with the single flange portion 52 defining a cutout portion 60'throughwhich a portion of the bottom roller 58 extends. The bottomroller 58 ispositioned between forward flange portion 34 and rearward flange portion36, with the rolling portions of that bottom roller 58 adjacent saidforward and rearward flange portions 34,36.

Bottom roller 62 is mounted to the lower end of the elongated member 46,with the single flange portion 56 defining a cutout portion 64 throughwhich a portion of the bottom roller 62 extends. The bottom roller 62 ispositioned between forward and rearward flange portions 40,42 with therolling portions of that bottom roller 62 adjacent such forward andrearward flange portions 40,42.

A top roller 66 is removably mounted to the upper end of the channelmember 24 (FIG. 8). with the forward flange portion 34 defining a cutoutportion 68 through which a portion of the top roller 66 extends, withthe rolling portion of the top roller 66 adjacent the single flange 42of the elongated member 44. A top roller 70 is removably mounted to theupper end of the channel member 26, with the forward flange portion 40defining a cutout portion 72 through which a portion of the top roller70 extends, with the rolling portion of the top roller 70 adjacent thesingle flange portion 56.

These cutout portions 60,64 are sized so that, in combination with thebottom rollers 58,62, the top rollers 66,70 are respectively blockedthereby so that they cannot be moved through cutout portions 66,64.Similarly, the cutout portions 68,72 are sized so that, in combinationwith the top rollers 66,70, the bottom rollers 58,62 are respectivelyblocked thereby so that they cannot be moved through cutout portions60,64. Consequently, with all rollers 58,62,66,'70 in place, the mastassembly so far described cannot be assembled if in a disassembledstate, or disassembled if in an assembled state.

The manner'of assembly of the structure is shown in FIGS. 9-10 and willrelate to channel member 26 and elongated member 46, it being understoodthat the operation is the same in relation to channel member 24 andelongated member 44, and is undertaken simultaneously with the operationon the corresponding parts associated with channel member 26 andelongated member 46.

Initially, top roller 70 is removed, and elongated member 46 ispositioned as shown in FIG. 9 relative to channel member 26, and moveddownwardly relative to channel member 26, removal of top roller 70allowing such positioning and movement, which would not be possible withtop roller 70 in place. Elongated member 46 is moved downwardly untiltop roller 76 can be fitted to channel member 26, the elongated member46being moved sufficiently downwardly to expose the top ends of channelmember 26 (FIG. I0).

In such manner, the assembly so far described allows movement of theelongated members 44,46 together along the channel members 24,26.

The channel member 24 defines an angled portion 74 which interconnectsthe base portion 32 and the rearward flange portion 36. The rollingportion of roller 58 is in position to contact the angled portion 74 andthe forward flange portion 34, as shown. Similarly, the channel member26 defines an angled portion 76 which interconnects the base portion 38and the rearward flange portion 42. The rolling portions of roller '62are in a position to contact the angled portion 76 and the forwardflange portion 40.

The elongated member 44 defines an angled portion 78 which interconnectsbase portion 56 and single flange portion 52 so that the rolling portionof the top roller 66 is in position to contact the angled portion 7 8.The elongated member 46 defines and angled portion 80 whichinterconnects base portion 54 and single flange portion 56, so that therolling portion of the top roller 70 is in position to contact saidangled portion 80.

in the assembly of said structure, the bottom rollers 58,62 are shimmedand then are run over the full length of travel before top rollers 66,70are installed, as described above.- In this way, the'installation ofbottom rollers 58,62 can be checked for proper operation inde pendentlyof the top rollers 66,70 subsequently installed in the channel members24,26. Proper operation of the top rollers 66,70 can then be checked byextending and retracting the structure again with all four rollers58,62, 66,70 in place.

Associated with the mast assembly 20 as a part thereof are load liftingmeans comprising a fork carriage 82. Said fork carriage 82 is made up ofa frame 83 and forwardly extending arms 85. Elongated member 44 has apair of parallel edge flange portions 84,86 extending from the baseportion 50 thereof, and generally perpendicular to the base portion 50thereof. Said pair of flange portions 84,86 are disposed toward theelongated member 46, as shown. Elongated member 46 has a pair ofparallel edge flange portions 88,90 extending from the base portion 54thereof, and generally perpendicular to the base portion 54. Said pairof flange portions 88,90 are disposed toward the elongated member 44.Said flange portions 84,88 are actually forward flange portions, andflange portions 86,90 are rearward flange portions.

The elongated member 44 defines an angled portion 92 which interconnectsthe base portion 50 and the rearward flange portion 86;, and theelongated member 46 similarly defines an'angled portion 94 whichinterconnects the base portion 54 and the rearward flange portion 90. w

Mounted to the frame 83 of fork carriage 82 are rollers 96,98,100,102.Rollers 96,98 are positioned be- --tween the flange portionsj84,86, withthe rolling portioned with its axis below the axis of roller 96 andabove the axis of roller 98. A roller 106 is also mounted to the frame83 and is positioned with its axis below the axis of roller 100 andabove the axis of roller 102. The rollers 104,106 are positioned tocontact the rearward flange portions 86,90 of the elongated members44,46 respectively, to provide positive lateral location of the forkcarriage 82 relatively to the elongated members The rollers 98,102 areshimmed so as to be positioned to contact the angled portions 92,94respectively. Said means allow movement of the fork carriage 82 alongthe elongated members 44,46 upwardly and downwardly, meanwhile providingpositive forward rearward locations of the fork carriage 82 relative tothe elongated members 44,46.

shimmed to bear on angled portion 92,94. With an off center load, theside thrust roller on one side of fork carriage 82 and the lower rolleron the other side of the fork carriage 82 handle 'the'tuming momentplaced on the fork carriage 82. With side thrusts in either direction,because of the placing of the rollers 104,106 to contact the rearwardflange portions 86,90 and the placing of rollers 98,102 to contactangled portions 92,94 which are themselves rearward, loads are appliedto the elongated members 44,46 as closely as possible to the rearportions thereof, where the cross braces 48 are fixed, so that there islittle tendency for the elongated members 44,46 to open up or spreadapart upon such application of side thrust thereto. The particularplacing of the rollers 104,106 relative to rollers 98,96-

and rollers 102,100 respectively, aids in such stability and strength.in addition, rollers 104,106 can be used as fork carriage 82 stops ifdesired, eliminating the need for separate parts. i

It will be seen that herein is provided a mast assembly which is ofcompact arrangement in the fully lowered position, meanwhile beingraisable to allow sufficient extension thereof. The roller systemincorporated and the particular positioning thereof insure thateccentric loading is properly carried, meanwhile also insuringsmoothness of operation under this and all other conditions. Suchdesign, as will be seen, is also simple, and lends itself to ease ofmanufacture.

What is claimed is:

1. A mast assembly for a truck or the like, comprising:

first and second upright laterally spaced channel members each defininga base portion and forward and rearward parallel edge flange portionextending from said base portion and generally perpendicular thereto,with the flange portions of each channel member disposed toward theother channel member; first and second interconnected elongated memberspositioned inwardly of the first and second channel members respectivelyand movable therealong, the

first elongated member defining a base portion and an edge flangeportion extending from said base portion and generallyperpendicularthereto, and disposed towardthe first channel member and between theforward and rearward flange portions of the first channel member andadjacent the rearward flange portion thereof, the second elongatedmember defining a base portion and an edge flange portion disposedtoward the second channel member and between the forward and rearwardflange portions of the'second channel member and adjacent the rearwardflange portion thereof; first and second bottom rollers mounted to thelower ends of the first and second elongated members respectively, theedge flange portions of the first and second elongated members definingcutout portions through whichportions of the first and second bottomrollers respectively extend, with the first bottom roller positionedbetween the forward and rearward flange portions of the first channelmember, with the rolling portions of the first bottom roller adjacentthe forward and rearward flange portions of the first channel member,and further with the second bottom roller positioned between the forwardand rearward flange portions of the second channel member, with therollingportions of the second bottom roller adjacent the forward andrearward flange portions of the second channel member;

first and second top rollers mounted to the upper ends of the first andsecond channel members respectively, with the forward flange portions ofthe first and second channel members defining cutout portions throughwhich portions of the first and second top rollers respectively extend,with the rollingportion of the first top roller adjacent the edge flangeportion of the first elongated member, and with the rolling portion ofthe second top roller adjacent the edge flange portion of the secondelongated member;

a fork carriage comprising a frame and a pair of forwardly extendingarms;

first and second rollers mounted to the fork carriage frame androllingly associated with the first elongated member, with the axis ofthe second roller being below the axis of the first roller;

third and fourth rollers mounted to the fork carriage frame androllingly associated with the second elongated member, with the axis ofthe fourth roller being below the axis of the third roller, allowingmovement of the fork carriage along the elongated members upwardly anddownwardly, meanwhile providing positive forward-and-rearward locationof the fork carriage relative to the first and second elongated members;

a fifth roller mounted to fork carriage frame and positioned with itsaxis below the axis of the first roller and above the axis of the secondroller; and,

a sixth roller mounted to the fork carriage frame and positioned withits axis below the axis of the third roller and above the axis of thefourth roller, the fifth and sixth rollers being in contact with therear portions of the first and second elongated member respectivelyinwardly of the first and second elongated members respectively, and areinforcing member interconnecting the first and second elon gatedmembers rearwardly thereof, the fifth and sixth rollers passing closelyadjacent thereto to minimize misalignment of said elongated members, toprovide positive lateral location of the fork carriage relative to thefirst and second elongated members.

2. Load lifting apparatus comprising: i

first and'second laterally spaced apart elongated members; a forkcarriage comprising a frame and a pair of forwardly extending arms;

' first and second rollers mounted to the fork carriage a fifth rollermounted to the fork carriage frame and positioned with its axis belowthe axis of the first roller and above the axis of the second roller,and,

a sixth roller mounted to the fork carriage frame and positioned withits axis below the axis of the third roller and above the axis of thefourth roller. the fifth and sixth rollers being in contact with therear portions of the first and second elongated members respectivelyinwardly of the first and second elongated members respectively, and areinforcing member interconnecting the first and second elongatedmembers rearwardly thereof, the fifth and sixth rollers passing closelyadjacent thereto to minimize misalignment of said elongated members, toprovide positive lateral location of the fork carriage relative to thefirst and second elongated members.

3. The load lifting apparatus of claim 2 wherein the axis of the secondroller is substantially directly below the axis of the first roller, andwherein the axis of the fourth roller is substantially directly belowthe axis of the third roller.

4. The load lifting apparatus of claim 3 wherein the first elongatedmember comprises a base portion and a pair of parallel edge flangeportions extending from the base portion, with the first and secondrollers positioned between the pair of parallel flange portions of thefirst elongated member and having the rolling portionsv thereof adjacentsaid pair of flange portions of the first elongated member, and whereinthe second elongated member comprises a base portion and a pair ofparallel edge flange portions extending from the base portion, with thethird and fourth rollers positioned between the parallel flange portionsof the second elongated member and having the rolling portions thereofadjacent said pair of flange portions of the second elongated member.

5. The load lifting apparatus of claim 4 wherein the pair of flangeportions of the first elongated member comprise forward and rearwardflange portions disposed toward the second elongated member, and whereinthe pair of flange portions of the second elongated member compriseforward and rearward flange portions disposed toward the first elongatedmember.

6. The load lifting apparatus of claim 5 wherein the fifth roller is incontact with the rearward flange portion of the first elongated member,and thesixth roller is in contact with the rearward flange portion ofthe second elongated member.

7. The load lifting apparatus of claim 6 wherein the pair of flangeportions of the first elongated member are generally perpendicular tothe base portion thereof, and the pair-of flange portions of the'secondelongated member'are generally perpendicular to the base portionthereof.

8. The load lifting apparatus of claim 7 wherein the first elongatedmember defines a first angled portion interconnecting the base portionand oneof the pair of flange portions thereof, so that the rollingportions of the second roller are in position to contact said firstangle d portion and the other of the pair of flange portions of thefirst elongated member, and wherein the second elongated member definesa second angled portion interconnecting the base portion and one of thepair of flange portions thereof, so that the rolling portions of thefourth roller are in position to contact the second angled portion andthe other of the pair of flange portions of the second elongated member.

9. A load lifting apparatus of claim 8 wherein the first angled portioninterconnects the base portion and the rearward flange portion ofthefirst elongated member, and wherein the second angled portioninterconnects the base portion and the rearward flange portion of thesecond elongated member.

10. A mast assembly for a truck or the like, comprising:

first and second upright, laterally spaced channel members, eachdefining a base portion and forward and rearward parallel edge flangeportions extending from said base portion and generally perpendicularthereto, with the flange portions of each channel member disposed towardthe other channel member;

first and second interconnected elongated members positioned inwardly ofthe first and second channel members respectively and movabletherealong, the

first elongated member defining a base portion and tween the forward andrearward flange portions of the first channel member and adjacent therearward flange portion thereof, the'second elongated member defining abase portions and an edge flange portion disposed toward the secondchannel member and between the forward and rearward flange portions ofthe second channel member and adjacent the rearward flange. portionthereof;

first and second bottom rollers mounted to the lower ends of the firstand second elongated members respectively, the edge flange portions ofthe first and second elongated members defining cutout portions throughwhich portions of the first and second bottom rollers respectivelyextend, with the first bottom roller positioned between the forward andrearward flange portions of the first channel member, with the rollingportions of the first bottom roller adjacent the forward and rearwardflange portions of the first channel member, and further with the secondbottom roller positioned between the forward and rearward flangeportions of the second channel member, with the rolling portions of thesecond bottom roller adjacent the forward and rearward flange portionsof the second channel member;

first and second top rollers mounted to the upper ends of the first andsecond channel members respectively, with the forward flange portions ofthe first and second channel member defining cutout portions throughwhich portions of the first and second top rollers respectively extend,with the rolling portion of the first top roller adjacent the edgeflange portion of the first elongated member,

and with the rolling portion of the second top roller adjacent the edgeflange portion of the second elongated member, wherein the first andsecond top rollers are removably mounted to the upper ends of the firstand second channel members respectively, wherein, with the first andsecond top rollers and first and second bottom rollers so mounted, thecutout portions of the edge flange portions of the first and secondelongated members are sized, in combination with the first and secondbottom rollers, to block passage of the first and second top rollersrespectively therethrough, and the cutout portions of the forward flangeportions of the first and second channel members are sized. incombination with the first and second top rollers. to block passage ofthe first and second bottom rollers respectively therethrough. ll. Themast assembly of claim 10 wherein the first channel member defines anangled portion interconnecting the base portion and the rearward flangeportion thereof, so that the rolling portions of the first bottom rollerare in a position to contact said first channel member angled portionand the forward flange portion thereof, and wherein the second channelmember defines an angled portion interconnecting the base portion andthe rearward flange portion thereof, so that the rolling portions of thesecond bottom roller are in a position to contact said second channelmember angled portion and the forward'flange portion thereof, andwherein the first elongated member defines an angled portioninterconnecting the base portion thereof and the edge flange portionthereof, so that the rolling portion of the first top roller is inposition to contact said first elongated member angled portion. andwherein the second elongated member defines an angled portioninterconnecting the baseportion thereof and the edge flange portionthereof, so that the rolling portion of the second top roller is inposition to contact the second elongated member angled portion.

12. The mast assembly of claim 11 and further comprising:

a fork carriage comprising a frame and a pair of for wardly extendingarms;

first and second rollers mounted to the fork carriage frame androllingly associated with the first elongated member, with the axis ofthe second roller being below the axis of the first roller;

third and fourth rollers mounted to the fork carriage frame androllingly associated with the second elongated member, with the axis ofthe fourth 'roller being below the axis of the third roller, allowingmovement of the fork carriage along the'elongated members upwardly anddownwardly, meanswhile providing positive forward-and-rearward locationof the fork carriage relative to the first and second elongated members;

a fifth roller mounted to the fork carriage frame and positioned withits axis below the axis of the first roller and above the axis of thesecond roller; and,

a sixth roller mounted to the fork carriage frame and positioned withits axis below the axis of the third roller and above the axis of thefourth roller, the fifth and sixth rollers being in contact with therear portions of the first and second elongated members inwardly of thefirst and second elongated members respectively to provide positivelateral location of the fork carriage relative to the first and sec- 1 1base portion, with the first and second rollers positioned between thepair of parallel flange portions of the first elongated member andhaving the rolling portions thereof adjacent said pair of flangeportions of the first elongated member, and wherein the second elongatedmember comprises a base portion and a pair of parallel edge flangeportions extending from the base portion, with the third and fourthrollers positioned between the parallel flange portions of the secondelongated member and having the rolling portions thereof adjacent saidpair of flange portions of the second elongated member.

15. The load lifting apparatus of claim 14 wherein the pair of flangeportions of the first elongated member comprise forward and rearwardflange portions disposed toward the second elongated member, and whereinthe pair of flange portions of the second elongated member compriseforward and rearward flange portions disposed toward a first elongatedmember.

16. The load lifting apparatus of claim 15 wherein the fifth roller isin contact with the rearward flange portion of the first elongatedmember, and the sixth roller is in contact with the rearward flangeportion of the second elongated member. 7

17. The load lifting apparatus of claim 16 wherein the pair of flangeportions of the first elongated member are generally perpendicular tothe base portion thereof, and the pair of flange portions of the secondelongated member are generally perpendicular to the base portionthereof.

18. The load lifting apparatus of claim 17 wherein the first elongatedmember defines a first angled portion interconnecting the base portionand one of the pair of flange portions thereof, so that the rollingportions of the second roller are in position to contact said firstangled portion and the other of the pair of flange portions of the firstelongated member, and wherein the second elongated member defines asecond angled portion interconnecting the base portion and one of thepair of flange portions thereof, so that the rolling portions of thefourth roller are in position to contact the second angled portion andthe other of the pair of flange portions of the second elongated member.

19. A load lifting apparatus of claim 18 wherein the first angledportion interconnects the base portion and the rearward flange portionof the firstelongated member, and wherein the second angled portioninterconnects the base portion and the rearward flange portion of thesecond elongated member.

1. A mast assembly for a truck or the like, comprising: first and secondupright laterally spaced channel members each defining a base portionand forward and rearward parallel edge flange portion extending fromsaid base portion and generally perpendicular thereto, with the flangeportions of each channel member disposed toward the other channelmember; first and second interconnected elongated members positionedinwardly of the first and second channel members respectively andmovable therealong, the first elongated member defining a base portionand an edge flange portion extending from said base portion andgenerally perpendicular thereto, and disposed toward the first channelmember and between the forward and rearward flange portions of the firstchannel member and adjacent the rearward flange portion thereof, thesecond elongated member defining a base portion and an edge flangeportion disposed toward the second channel member and between theforward and rearward flange portions of the second channel member andadjacent the rearward flange portion thereof; first and second bottomrollers mounted to the lower ends of the first and second elongatedmembers respectively, the edge flange portions of the first and secondelongated members defining cutout portions through which portions of thefirst and second bottom rollers respectively extend, with the firstbottom roller positioned between the forward and rearward flangeportions of the first channel member, with the rolling portions of thefirst bottom roller adjacent the forward and rearward flange portions ofthe first channel member, and further with the second bottom rollerpositioned between the forward and rearward flange portions of thesecond channel member, with the rolling portions of the second bottomroller adjacent the forward and rearward flange portions of the secondchannel member; first and second top rollers mounted to the upper endsof the first and second channel members respectively, with the forwardflange portions of the first and second channel members defining cutoutportions through which portions of the first and second top rollersrespectively extend, with the rolling portion of the first top rolleradjacent the edge flange portion of the first elongated member, and withthe rolling portion of the second top roller adjacent the edge flangeportion of the second elongated member; a fork carriage comprising aframe and a pair of forwardly extending arms; first and second rollersmounted to the fork carriage frame and rollingly associated with thefirst elongated member, with the axis of the second roller being belowthe axis of the first roller; third and fourth rollers mounted to thefork carriage frame and rollingly associated with the second elongatedmember, with the axis of the fourth roller being below the axis of thethird roller, allowing movement of the fork carriage along the elongatedmembers upwardly and downwardly, meanwhile providing positiveforward-and-rearward location of the fork carriage relative to the firstand second elongated members; a fifth roller mounted to fork carriageframe and positioned with its axis below the axis of the first rollerand above the axis of the second roller; and, a sixth roller mounted tothe fork carriage frame and positioned with its axis below the axis ofthe third roller and above the axis of the fourth roller, the fifth andsixth rollers being in contact with the rear portions of the first andsecond elongated member respectively inwardly of the first and secondelongated members respectively, and a reinforcing member interconnectingthe first and second elongated members rearwardly thereof, the fifth andsixth rollers passing closely adjacent thereto to minimize misalignmentof said elongated members, to provide positive lateral location of thefork carriage relative to the first and second elongated members. 2.Load lifting apparatus comprising: first and second laterally spacedapart elongated members; a fork carriage comprising a frame and a pairof forwardly extending arms; first and second rollers mounted to thefork carriage frame and rollingly associated with the first elongatedmember, with the axis of the second roller being below the axis of thefirst roller; thrid and fourth rollers mounted to the fork carriageframe and rollingly associated with the second elongated member, withthe axis of the fourth roller being below the axis of the thrid roller,allowing movement of the fork carriage along the elongated membersupwardly and downwardly, meanwhile providing positiveforward-and-rearward location of the fork carriage relative to the firstand second elongated members; a fifth roller mounted to the forkcarriage frame and positioned with its axis below the axis of the firstroller and above the axis of the second roller, and, a sixth rollermounted to the fork carriage frame and positioned with its axis belowthe axis of the third roller and above the axis of the fourth roller,the fifth and sixth rollers being in contact with the rear portions ofthe first and second elongated members respectively inwardly of thefirst and second elongated members respectively, and a reinforcingmember interconnecting the first and second elongated members rearwardlythereof, the fifth and sixth rollers passing closely adjacent thereto tominimize misalignment of said elongated members, to provide positivelateral location of the fork carriage relative to the first and secondelongated members.
 3. The load lifting apparatus of claim 2 wherein theaxis of the second roller is substantially directly below the axis ofthe first roller, and wherein the axis of the fourth roller issubstantially directly below the axis of the third roller.
 4. The loadlifting apparatus of claim 3 wherein the first elongated membercomprises a base portion and a pair of parallel edge flange portionsextending from the base portion, with the first and second rollerspositioned between the pair of parallel flange portions of the firstelongated member and having the rolling portions thereof adjacent saidpair of flange portions of the first elongated member, and wherein thesecond elongated member comprises a base portion and a pair of paralleledge flange portions extending from the base portion, with the third andfourth rollers positioned between the parallel flange portions of thesecond elongated member and having the rolling portions thereof adjacentsaid pair of flange portions of the second elongated member.
 5. The loadlifting apparatus of claim 4 wherein the pair of flange portions of thefirst elongated member comprise forward and rearward flange portionsdisposed toward the second elongated member, and wherein the pair offlange portions of the second elongated member comprise forward andrearward flange portions disposed toward the first elongated member. 6.The load lifting apparatus of claim 5 wherein the fifth roller is incontact with the rearward flange portion of the first elongated member,and the sixth roller is in conTact with the rearward flange portion ofthe second elongated member.
 7. The load lifting apparatus of claim 6wherein the pair of flange portions of the first elongated member aregenerally perpendicular to the base portion thereof, and the pair offlange portions of the second elongated member are generallyperpendicular to the base portion thereof.
 8. The load lifting apparatusof claim 7 wherein the first elongated member defines a first angledportion interconnecting the base portion and one of the pair of flangeportions thereof, so that the rolling portions of the second roller arein position to contact said first angled portion and the other of thepair of flange portions of the first elongated member, and wherein thesecond elongated member defines a second angled portion interconnectingthe base portion and one of the pair of flange portions thereof, so thatthe rolling portions of the fourth roller are in position to contact thesecond angled portion and the other of the pair of flange portions ofthe second elongated member.
 9. A load lifting apparatus of claim 8wherein the first angled portion interconnects the base portion and therearward flange portion of the first elongated member, and wherein thesecond angled portion interconnects the base portion and the rearwardflange portion of the second elongated member.
 10. A mast assembly for atruck or the like, comprising: first and second upright, laterallyspaced channel members, each defining a base portion and forward andrearward parallel edge flange portions extending from said base portionand generally perpendicular thereto, with the flange portions of eachchannel member disposed toward the other channel member; first andsecond interconnected elongated members positioned inwardly of the firstand second channel members respectively and movable therealong, thefirst elongated member defining a base portion and an edge flangeportion extending from said base portion and generally perpendicularthereto, and disposed toward the first channel member and between theforward and rearward flange portions of the first channel member andadjacent the rearward flange portion thereof, the second elongatedmember defining a base portions and an edge flange portion disposedtoward the second channel member and between the forward and rearwardflange portions of the second channel member and adjacent the rearwardflange portion thereof; first and second bottom rollers mounted to thelower ends of the first and second elongated members respectively, theedge flange portions of the first and second elongated members definingcutout portions through which portions of the first and second bottomrollers respectively extend, with the first bottom roller positionedbetween the forward and rearward flange portions of the first channelmember, with the rolling portions of the first bottom roller adjacentthe forward and rearward flange portions of the first channel member,and further with the second bottom roller positioned between the forwardand rearward flange portions of the second channel member, with therolling portions of the second bottom roller adjacent the forward andrearward flange portions of the second channel member; first and secondtop rollers mounted to the upper ends of the first and second channelmembers respectively, with the forward flange portions of the first andsecond channel member defining cutout portions through which portions ofthe first and second top rollers respectively extend, with the rollingportion of the first top roller adjacent the edge flange portion of thefirst elongated member, and with the rolling portion of the second toproller adjacent the edge flange portion of the second elongated member,wherein the first and second top rollers are removably mounted to theupper ends of the first and second channel members respectively,wherein, with the first and second top rollers and first and secondbottom rollers so mounted, the cutout portionS of the edge flangeportions of the first and second elongated members are sized, incombination with the first and second bottom rollers, to block passageof the first and second top rollers respectively therethrough, and thecutout portions of the forward flange portions of the first and secondchannel members are sized, in combination with the first and second toprollers, to block passage of the first and second bottom rollersrespectively therethrough.
 11. The mast assembly of claim 10 wherein thefirst channel member defines an angled portion interconnecting the baseportion and the rearward flange portion thereof, so that the rollingportions of the first bottom roller are in a position to contact saidfirst channel member angled portion and the forward flange portionthereof, and wherein the second channel member defines an angled portioninterconnecting the base portion and the rearward flange portionthereof, so that the rolling portions of the second bottom roller are ina position to contact said second channel member angled portion and theforward flange portion thereof, and wherein the first elongated memberdefines an angled portion interconnecting the base portion thereof andthe edge flange portion thereof, so that the rolling portion of thefirst top roller is in position to contact said first elongated memberangled portion, and wherein the second elongated member defines anangled portion interconnecting the base portion thereof and the edgeflange portion thereof, so that the rolling portion of the second toproller is in position to contact the second elongated member angledportion.
 12. The mast assembly of claim 11 and further comprising: afork carriage comprising a frame and a pair of forwardly extending arms;first and second rollers mounted to the fork carriage frame androllingly associated with the first elongated member, with the axis ofthe second roller being below the axis of the first roller; third andfourth rollers mounted to the fork carriage frame and rollinglyassociated with the second elongated member, with the axis of the fourthroller being below the axis of the third roller, allowing movement ofthe fork carriage along the elongated members upwardly and downwardly,meanswhile providing positive forward-and-rearward location of the forkcarriage relative to the first and second elongated members; a fifthroller mounted to the fork carriage frame and positioned with its axisbelow the axis of the first roller and above the axis of the secondroller; and, a sixth roller mounted to the fork carriage frame andpositioned with its axis below the axis of the third roller and abovethe axis of the fourth roller, the fifth and sixth rollers being incontact with the rear portions of the first and second elongated membersinwardly of the first and second elongated members respectively toprovide positive lateral location of the fork carriage relative to thefirst and second elongated members.
 13. The load lifting apparatus ofclaim 12 wherein the axis of the second roller is substantially directlybelow the axis of the first roller, and wherein the axis of the fourthroller is substantially directly below the axis of the third roller. 14.The load lifting apparatus of claim 13 wherein the first elongatedmember comprises a base portion and a pair of parallel edge flangeportions extending from the base portion, with the first and secondrollers positioned between the pair of parallel flange portions of thefirst elongated member and having the rolling portions thereof adjacentsaid pair of flange portions of the first elongated member, and whereinthe second elongated member comprises a base portion and a pair ofparallel edge flange portions extending from the base portion, with thethird and fourth rollers positioned between the parallel flange portionsof the second elongated member and having the rolling portions thereofadjacent said pair of flange portions of the second elongated member.15. The load lifting apparatus of claim 14 wherein the pair of flangeportions of the first elongated member comprise forward and rearwardflange portions disposed toward the second elongated member, and whereinthe pair of flange portions of the second elongated member compriseforward and rearward flange portions disposed toward a first elongatedmember.
 16. The load lifting apparatus of claim 15 wherein the fifthroller is in contact with the rearward flange portion of the firstelongated member, and the sixth roller is in contact with the rearwardflange portion of the second elongated member.
 17. The load liftingapparatus of claim 16 wherein the pair of flange portions of the firstelongated member are generally perpendicular to the base portionthereof, and the pair of flange portions of the second elongated memberare generally perpendicular to the base portion thereof.
 18. The loadlifting apparatus of claim 17 wherein the first elongated member definesa first angled portion interconnecting the base portion and one of thepair of flange portions thereof, so that the rolling portions of thesecond roller are in position to contact said first angled portion andthe other of the pair of flange portions of the first elongated member,and wherein the second elongated member defines a second angled portioninterconnecting the base portion and one of the pair of flange portionsthereof, so that the rolling portions of the fourth roller are inposition to contact the second angled portion and the other of the pairof flange portions of the second elongated member.
 19. A load liftingapparatus of claim 18 wherein the first angled portion interconnects thebase portion and the rearward flange portion of the first elongatedmember, and wherein the second angled portion interconnects the baseportion and the rearward flange portion of the second elongated member.